Purple Pencilfish Care Guide - Aquarium Setup, Diet & Breeding

Purple Pencilfish are delicate, streamlined characins with a slender, pencil-like profile and an attractive reddish-purple sheen. Their bodies are typically marked with dark horizontal lines, while the caudal fin and rear portion of the body can show rich red to violet colouring, especially in mature males and displaying individuals.

Despite their small size, these fish have a lively and graceful presence. They spend much of their time in the upper and middle levels of the aquarium, hovering among plants and making quick, controlled movements rather than constantly darting across open water.

In the wild, Nannostomus rubrocaudatus inhabits quiet forest waterways influenced by fallen leaves, submerged branches and overhanging vegetation. The subdued light and tannin-stained surroundings provide both shelter and a background that accentuates their vivid colours.

Purple Pencilfish are peaceful shoaling fish with interesting social behaviour. Males may posture and display to one another, showing stronger colour when competing for attention or courting females, while a group moving together creates a particularly attractive, natural-looking display.

Purple Pencilfish are native to the upper Amazon region of Peru in South America, where they occur in slow-moving forest streams, tributaries and blackwater environments. The species is associated with clear to tea-coloured water shaded by dense rainforest vegetation.

A group of Purple Pencilfish should be given an aquarium of at least 40 litres, with a footprint around 60 by 30 cm providing more useful swimming space than a tall tank. Use gentle filtration and subdued lighting, with dense planting around the sides and back, open water for shoaling, and floating plants to diffuse the light. A dark, fine-grained substrate, driftwood, leaf litter and smooth branches help recreate their shaded forest-stream habitat. Keep the aquarium mature, stable and well covered, as these slender fish can jump.

Up to about 3.5 cm (1.4 in) in standard length; females are usually slightly larger and fuller-bodied than males.

Purple Pencilfish are small omnivores and should receive a varied diet of fine flake, micro-pellets and appropriately sized frozen or live foods. They particularly appreciate baby brine shrimp, daphnia, cyclops and other tiny zooplankton, while occasional foods such as mosquito larvae can help condition adults for breeding. Offer small portions several times a day so every fish can eat without excessive waste.

Purple Pencilfish are well suited to peaceful community aquariums containing similarly small, calm species. Suitable companions include small rasboras, ember tetras, other gentle tetras, pencilfish, otocinclus and small Corydoras. Avoid large, boisterous or predatory fish, fin-nippers and highly competitive feeders, which may intimidate them or outcompete them for food. They are also best kept away from aggressive cichlids and other fish large enough to swallow them.

Purple Pencilfish are egg-scattering fish that breed most readily in a mature, dimly lit aquarium with soft, acidic water. Condition a group with plenty of live or frozen foods, then place a pair or small group in a dedicated breeding tank containing fine-leaved plants or spawning mops. Adults may eat the eggs, so remove them after spawning or protect them with a mesh divider. The eggs usually hatch in around 24 to 36 hours, and the tiny fry need infusoria or another suitably fine first food before they can accept newly hatched brine shrimp.

Males are generally slimmer and more intensely coloured, particularly through the purple-red body and caudal region, and they develop stronger colour during displays. Females tend to be slightly larger with a deeper, rounder abdomen, especially when carrying eggs.